You can make a "plate" out of aome 1/8" fiber board or ABS plastic(or they sell they sell the plate adapters by Metra) . I usually buy my speaker wire in a 500 or 1000 ft roll but you can buy a 100 foot roll so you dont run short. It depends on the speakers i am wiring for the size. I use 12 or 14 GA for subs and 16 or 16 GA for mids and highs.
Metra makes the speaker adapters, Any stereo shop should stock this. I have Kicker RS 6.5 components in my door. Your going to have to fab the tweeters in the fac. tweeter pod somehow. It's super easy. I used back strapping. The 250/1 is what is recommended by JL for the stealthbox. Perfect match up. The 500/1 is too much.